The present invention relates to a control method and a control device for an automatic transmission control system in an automobile.
The automobile of a manual transmission has excellent fuel economy compared with one having a transmission based on a torque converter. Recently, an automatic manual transmission (automatic MT) has been developed, which is designed to perform automatic clutch or gear changing by using the mechanism of the manual transmission. However, during the control of speed changing in the conventional automatic MT, fluctuation occurred in acceleration because of the releasing/connecting of a first friction clutch provided to disconnect/connect torque transmission between an engine and the transmission, giving an unnatural feeling to an occupant. This problem led to the disclosure of an automatic transmission, which includes a second friction clutch (assist clutch) provided between the input and output shafts of the transmission to carry out torque transmission during the speed changing of the conventional automatic MT, as described in Japanese Patent Application Laid-open No. 65199/2000. In the control of speed changing by the automatic Mt having such an assist clutch, the assist clutch is pressed to carry out torque transmission from the connected state of a claw clutch at the starting time of the speed changing while the assist clutch is slid. The claw clutch is released after the completion of predetermined torque transmission. As exemplified by the system just noted above, torque transmission is realized during speed changing by switching to the assist clutch from the claw clutch at the starting time of the speed changing.
However, the claw clutch allows only ON-OFF operations to be performed for setting connected and disconnected states. Hence, if the claw clutch is released while torque transmission by the assist clutch is insufficient or excessive, large torque fluctuation occurs during the releasing of the claw clutch, resulting in the deterioration of comfortableness. This problem necessitates the accurate setting of a timing for switching between the claw clutch and the assist clutch. With regard to the torque transmission characteristic of the assist clutch, however, a constant friction state is not provided. To explain, friction state variance occurs because of the change of a friction material with time, the change of an oil characteristic in the case of a wet clutch, a temperature characteristic, and so on. Under these circumstances, a change is inevitable in the switching timing, and comfortableness is deteriorated depending on the state.
Therefore, an object of the present invention is to provide a learning method, and another object of the present invention is to provide a learning device for an automatic transmission control system which is designed to optimize a timing for switching between an assist clutch and a claw clutch during speed changing and which is capable of preventing the deterioration of comfortableness due to a change with time and so on by optimizing each timing for switching between the claw clutch and the assist clutch.
In order to achieve one of the above objects, according to the invention, there is provided a control method comprising the steps of: pressing an assist clutch while a claw clutch is connected base on a speed changing command; performing torque transmission by the assist clutch; and then releasing the claw clutch by a predetermined timing. In this case, a releasing timing is corrected by making determination as to whether the timing for releasing the claw clutch has been fastor slow according to the rotational speed of an output shaft after the releasing of the claw clutch.
In order to achieve the other of the foregoing objects, according to the invention, there is provided a control device for pressing an assist clutch while a claw clutch is connected based on a speed changing command, performing torque transmission by the assist clutch, and then releasing the claw clutch by a predetermined timing. In this case, the control device comprises learning control means for measuring the rotational speed of the output shaft of a transmission, determining whether a timing for releasing the claw clutch has been fast or slow, and then correcting the releasing timing according to the results of the determination.
The foregoing constitution enables determination to be made as to whether the timing for releasing the claw clutch has been fast or slow according to a change in the rotational speed of the output shaft of the transmission, and the releasing timing to be corrected accordingly. Since the occurrence of torque fluctuation during switching between the assist clutch and the claw clutch can be detected, and each releasing timing of the claw clutch can be corrected based on the results of the detection, it is possible to prevent the great deterioration of comfortableness.
Furthermore, in order to achieve the foregoing object, according to the invention, the releasing timing is corrected by making determination as to whether the timing for releasing the claw clutch has been fast or slow according to the torque of the output shaft after the releasing of the claw clutch.
Also, in order to achieve the foregoing object, according to the invention, learning control means is provided for measuring the torque of the output shaft of the transmission, determining whether the timing for releasing the claw clutch has been fast or slow, and correcting the releasing timing based on the results of the determination.
Still further, in order to achieve the foregoing object, according to the invention, determination is made as to whether the timing for releasing the claw clutch has been fast or slow according to the acceleration of a vehicle after the releasing of the claw clutch, and then the releasing timing is corrected.
Also, in order to achieve the foregoing object, according to the invention, learning control means is provided for measuring the acceleration of the vehicle, determining whether the timing for releasing the claw clutch has been fast or slow, and correcting the releasing timing based on the results of the determination.
The foregoing constitution enables determination to be made as to whether the timing for releasing the claw clutch has been fast or slow according to a change in the torque of the output shaft of the transmission, a change in the acceleration of the vehicle, and so on, and the releasing timing to be corrected accordingly. Since the occurrence of torque fluctuation during switching between the assist clutch and the claw clutch can be detected, and each releasing timing of the claw clutch can be corrected based on the results of the detection, it is possible to prevent the great deterioration of comfortableness.